Telegram is Russia’s smartphone app of the moment, in more ways than one. The secretive messaging app has not spent a moment out of the limelight in recent days. It has been picked apart on national airtime, discussed in the Kremlin and topped sales in Russia’s Apple App Store as the country’s most popular software in stock.

Even considering the relative popularity Telegram enjoyed, the surge has been significant—only last week it was 15th, according to Russian business daily Vedomosti. Everyone from Russian President Vladimir Putin’s spokesman to Russia’s top newscasters are talking about Telegram—and whether it will be banned.

On the surface Telegram’s interface looks no different to other messengers like WhatsApp. Indeed, a user could easily send a message without noticing the difference. But Telegram’s secret chats are the source of much of its popularity, as well as its infamy.

Like Whatsapp, Telegram offers an encrypted messenger service, which allows users to converse with supposedly no record of their exact interaction on the company’s own servers. Its Secret Chats functions benefit from this end-to-end encryption and also allow users to set Mission Impossible-style self-destruct timers on their messages that range from two seconds to one week.

This means that even users themselves can be prevented from loading an old message if it has passed the expiration date set by its author.

Telegram is “transforming more and more into a system of communication for terrorism” Dmitry Kiselyov, one of Russia’s most renowned state TV journalists—often ridiculed as a telepropagandist for the Kremlin— announced last week. His weekly programme, usually focusing on political events with a strongly pro-Putin slant, took a rare dive into the world of tech.

The reason for the detour was that the app was under threat from Russia’s communications watchdog, Roskomnadzor, to be potentially banned if it did not register servers with user data and conversations in Russia.

Over the past three years Russia has introduced but selectively enforced a law that bans web services that store data of Russian users outside the jurisdiction of Russian law enforcement. Telegram, if slapped with a Russia-wide blackout, would be one of the most high profile casualties of the law to date.

Russia’s federal security services (FSB) announced on Monday that Telegram had been used during April’s deadly metro bombing in St. Petersburg and shifted the public attention on one of Telegram’s most controversial purposes, as a communication tool for criminals and extremists.

“Most actively, members of international terrorist organizations on the Russian Federation’s territory are using the Telegram messenger, providing them with the ability of creating secret chats with high level encryption, carrying information,” an FSB statement read.

However convenient the timing of the statement, Telegram has been used by extremist and criminal groups, whose chats usually require an invitation to join. Telegram’s strategy has been to close channels reported as extremist, but it is difficult to stop new chats popping up with similar content.

It is designed to shutout the FSB

Telegram is not only popular with the Russian public, but its leaders too. Putin allies such as Chechen leader Ramzan Kadyrov and officials within the Kremlin itself apparently use it, Putin’s spokesman Dmitry Peskov said on Monday that if the messenger service is banned “we will move onto another one,” state news agency Itar-Tass reported.

The app is designed by Russian social media gurus, the Durov brothers, with Russia in mind specifically, intended to foil prying law enforcement officials from reading people’s private messages.

“The No. 1 reason for me to support and help launch Telegram was to build a means of communication that can’t be accessed by the Russian security agencies, so I can talk about it for hours,” Pavel Durov told Techcrunch in 2014.

Bur Durov fell out with Russia’s state establishment long before Telegram. He first came to fame as the founder of Russia’s most popular social media site, VKontakte, which he ran until an acrimonious departure in 2014.

Prior to his leaving, Durov incurred the wrath of aurhorities as he refused to take down VKontakte groups promoting anti-Putin protests in 2012. Upon his sale of his shares and almost immediate firing as CEO in 2014, Durov left Russia, lamenting that the company was fully under the control of one of Putin’s closest allies Igor Sechin and internet magnate Alisher Usmanov, someone with a much more amicable relationship with the authorities than Durov.